Reviewing Powerful Ideas

We began class today by reviewing where we have been and where we are headed with class. We reviewed the powerful ideas we have learned so far:

• Light rays leave a source in all directions
  
• Light rays travel in straight lines
  
• Light rays bounce off smooth objects like mirrors in a regular way (angle of incidence = angle of reflection)
  
• Light rays bounce off rough objects in all directions
  
• For someone to see an object, light rays must enter the eye
  
• Light rays form the sides of similar triangles in pinhole cameras: H/D = h/d
  
• Objects left for a long time in a room reach the same temperature, room temperature
  
• Materials conduct heat and energy at different rates
  
• Heat flows from a heat source to colder objects
  
• Hot and cold water, when mixed together, come to a common temperature in between the hot temperature and the cold temperature; that is called the equilibrium temperature
  
• Change in temperature will be smaller for a bigger amount of water
  
• Change in temperature will be bigger for smaller amount of water
  
• Conservation of energy: heat lost = heat gained
  
• Heat energy lost by hot water: (mass of hot water)(T change of hot water)(c of water)
  
• Heat energy gained by cold water: (mass of cold water)(T change of cold water)(c of water)
  
• c is a property of materials called specific heat. Specific heat is the amount of heat energy needed to raise the temperature of one gram of the material by one degree Celsius.
• Water is a standard: c = 1 calorie is needed to raise the temperature of 1 gram of water (at 1 atmosphere of air pressure) by 1 degree Celsius